The present invention relates in general to a field-emission display, and more particularly, to a method for configuring an opening of a shadow masking converging electrode of a tetra-polar field-emission display, so as to optimize the converging effect.
FIG. 1 shows a converging electrode of a conventional tetra-polar field-emission display. As shown, a substrate 11a having an anode electrode structure formed thereon is provided. The anode electrode structure has a first conductive layer 12a and a second conductive layer 13a enclosing the first conductive layer 12a therein. The first and second conductive layers 12a and 13a serves as the electrode layer 14a on which electron beams will impinge, so as to generate light. The field-emission display further includes a cathode electrode structure, which comprises a substrate 21a, a first insulating layer 22a on the substrate 21a, a gate conductive layer 23a on the first insulating layer 22a, a second insulating layer 24a on the gate conductive layer 23a, and a converging layer on the second insulating layer 24a. The converging layer 25a, the second insulating layer 24a, the gate conductive layer 23a, and the first insulating layer 22a are patterned to form a window 26a from which the substrate 21a is exposed. The area of substrate exposed by the window 26a is denoted by the numeral reference 27a as shown in FIG. 1. A first conductive layer 28a is then formed on the exposed substrate 26a, and a second conductive layer 29a is formed on the first conductive layer 28a, such that a gate electrode layer 30a is formed as shown.
The above structure is formed using a metal shadow mask, and the gate conductive layer 23a is formed with a specific thickness between about 50 microns to about 200 microns, which is relative thick compared to the converging electrode fabricated by photolithography or screen printing process. The metal shadow mask is advantageous on mass production, however, it has the following drawbacks in addition to the relative thick feature.
Firstly, the electron beam starts diffusing after being drained by the gate layer. Therefore, the thicker the converging layer is, the longer path the electron beam is to propagate through the converging electrode. As a result, a portion of the electrons is absorbed by the converging electrode, such that the current density is reduced.
Secondly, to avoid the loss of the electron beam, the opening of the converging electrode is designed larger than the opening of the gate layer. Thereby, the space between the apertures of the gate shadow mask is reduced, and it is difficult to implement high-resolution array.
Thirdly, when the opening of the converging electrode is larger than that of the gate layer, higher voltage is required for the converging electrode for converging the electron beam.
It is therefore a substantially need to provide a method for fabricate a field-emission display of which the absorption of electron beam by the converging electrode is reduced, which the voltage provided to the converging electrode is not increased.